The impact of low-molecular carboxylic acids on carbon dioxide corrosion of steel in underground gas production equipment in the Dnipro-Donetsk basin fields

Abstract The work carried out a set of experimental studies to reduce the activity of corrosion processes in underground well equipment. Corrosion of downhole equipment is a complex heterogeneous process. In the complex of factors influencing both magnitude and intensity of corrosion damage, low molecular weight water-soluble carboxylic acids play a significant role. The features of metal-carbon dioxide corrosion (CO 2 corrosion) in production well fluid have been established depending on low molecular weight carboxylic acids. It has been revealed that the influence of carboxylic acids in field wells in the initial period of development is reduced to the destruction of protective carbonate films formed as a result of carbon dioxide corrosion of the metal surface. The highest corrosion rate is at the beginning of droplet water condensation since the main factors influencing the corrosion rate (acid concentration and temperature) are greatest at this point. It has been established that the interaction of organic acids with metal occurs in the Dnipro-Donetsk basin fields at the temperature range of 90-110°C and a depth of 3000-3500 m. The interval of action of organic acids on the metal of tubing pipes depends on the regime constancy and operating time of the well. In constant mode, the effect of organic acids is limited to 100-150 m. The effect of corrosion under the influence of organic acids is especially pronounced in wells where the carbon dioxide content is insignificant. The influence of corrosion products on the process speed has been determined. Iron salts of carboxylic acids, formed as a result of corrosion during condensation of aqueous fluid in a well, are subsequently inhibitors of carbon dioxide corrosion of gas industry equipment.